Modeling morphodynamic evolution in alluvial estuaries

Abstract

All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publishers. Although all care is taken to ensure the integrity and quality of this publication and the information herein, no responsibility is assumed by the publishers nor the author for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein.Published by: CRC Press/Balkema PO Box 447, 2300 AK Leiden, the Netherlands e-mail: Pub.NL@taylorandfrancis.com www.crcpress.com -www.taylorandfrancis.co.uk -www.ba.balkema.nl Cover image: Computed morphodynamic evolution in a 320 km long tidal embayment with bank erosion after 0, 800 and 6400 years. AbstractEstuaries are valuable areas. Tidal flats, tidally varying water levels and the saltfresh water interface are characteristics that form a unique ecological environment, which is often of international importance. Local fishery, aquaculture and tourism are important sectors that profit from the estuarine richness. Additionally, numerous ports are situated along estuaries, forming the logistical link between ocean transport and the hinterland. It is of utmost importance to understand estuarine processes so that impact of human interference (like dredging) and long-term changes (like sea level rise or a changing discharge regime) can be estimated and evaluated.The main objective of this research is to investigate the governing processes and characteristics that drive morphodynamic evolution in alluvial estuaries by means of application of a process-based numerical model (Delft3D). The Delft3D model numerically solves the shallow water equations, which result in a detailed water level and velocity field at any moment and at any place in the model domain. This information is used to predict sediment transports and the resulting bathymetric evolution.The research starts from a highly schematized configuration (a rectangular tidal basin filled with uniform sand and forced by a semi-diurnal tide) to study characteristic morphodynamic evolution over millennia. In subsequent chapters more processes are added, autonomous behavior is restricted and the timescale is reduced, to finally end up with a model configuration that matches the geometry of a real alluvial estuary and a 'comprehensive' timescale that allows model validation with measured morphological developments. The case studies used for model validation are the Western Scheldt estuary in the Netherlands and San Pablo Bay in California, USA.The models described in the current research did not reach a state of equilibrium in the strict sense. During the simulations tide residual transports and morphodynamic evolution remain continuously present despite the constant forcing conditions. Nevertheless, model results show a decay in (the rates of) energy dissipation and tid...

A large scale morphodynamic process-based model of the Gironde estuary

“…Morphodynamic factors have been extensively applied in order to reduce the computational cost [van der Wegen and Roelvink, 2008]. Model predictions could be extended over geological time scales, leading to realistic as well as stable model results [van der Wegen, 2010]. However, this simplifying method introduces an additional source of uncertainty and becomes questionable in the presence of mixed sediment, where consolidation and biological processes interact at their own time scales.…”